Fulgurites

Even before man learned the secret of glassmaking, nature made glass in two ways. The heat of volcanic eruption fuses rocks and sand into a glass called obsidian. When lightning strikes sand, the heat fuses it into long, slender glass tubes called fulgurites. They are commonly called petrified lightning, or lightning sticks. The fulgurite is nature's glass... irregular in shape and nontransparent. It takes on a greenish color depending on the hue of the sand as the lightning strikes.

The fulgurites is very brittle and will break from the vibrations when digging or just the pressure from the sand itself. Fulgurites are all different shapes and sizes, and once they start down into the sand, they will branch off the main finger, just like a flash of lightning in the sky. While some are quite round and hollow, many are flattened and rough shaped because of the pressure exerted by the surrounding sand on the fulgurite at the time when it is very hot and plastic like. The insides are smooth and glassy. Most fulgurite glass is rich in silica, which perhaps was dissolved in the glass rather than simply fused.

Silver Lake is one of the few areas known for finding these fulgurites. Mac Wood's has one of the largest displays of fulgurites, including one piece that is 9 feet long.